This invention relates to multi-yarn machinery for producing fabric, such as tufting machines, and more particularly to the detecting of a deviation from a norm in the tension of a yarn end and to its identification.
Tufting machines such as those used to produce tufted carpet and like materials may employ upwardly of one thousand needles mounted for vertical reciprocation, each of which needles carries a separate individual yarn into cooperative relationship with a looper to produce the tufted pile. Due to various conditions such as creel snarl-ups, that is yarn snarling as it pulls off the creel cones, excessive tension in one or of a few yarns may occur. Moreover, the reverse condition, that being no tension or a broken yarn may likewise occur. In the production of tufted fabrics the high rate of output of these machines is such that a substantial length of material containing a fault due, for example, to a broken or tight end may be produced before the fault is evident with consequential loss due to the defective fabric. This problem has been recognized in the prior art and various prior art detecting devices are known. Examples of such detectors are illustrated in U.S. Pat. Nos. 3,221,682; 3,221,683; 3,764,773; 3,994,245 and 4,078,505. The prior art detectors however are directed toward either excessive tension or zero tension, i.e. broken yarn, and do not detect deviations on both sides of a norm of the tension in the yarn. Moreover, the known detectors do not provide an immediate readily visible indication of the fault.